Motor-pump assembly

ABSTRACT

A motor-pump assembly for providing pressure for a motor vehicle brake system actuation device with a pneumatic brake booster, including a pump and an electric motor driving the pump. The pump is a double diaphragm pump with two opposing working diaphragms each clamped between a pump housing and a working chamber cover to delimit a working chamber and which are movable by a crank drive having an eccentric and connecting rods. The connecting rods each have a connecting rod shank and a connecting rod eye and are mounted movably on the eccentrics by roller bearings. To provide a motor-pump assembly which meets requirements relating to acoustic comfort, a resilient decoupling is provided between each connecting rod eye and the roller bearing, which damps transmission of vibrations to the roller bearing in the connecting rod shank which occur on a force direction change on the rotation of the crank drive.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase Application of PCT/EP2011/062901, filed Jul. 27, 2011, which claims priority to German Patent Application No. 10 2010 062 160.9, filed Nov. 30, 2010, the contents of such applications being incorporated by reference herein.

FIELD OF THE INVENTION

The invention concerns a motor-pump assembly, in particular for providing pressure for a brake actuation device of a motor vehicle brake system with a pneumatic brake booster, in particular a vacuum brake booster, comprising a pump and an electric motor driving the pump, wherein the pump is provided as a double diaphragm pump with two opposing working diaphragms which are each clamped between a pump housing and a working chamber cover and thus delimit a working chamber and which are movable by means of a crank drive having an eccentric and connecting rods, and wherein the connecting rods each have a connecting rod shank and a connecting rod eye of plastic and are mounted movably on the eccentrics by means of roller bearings.

BACKGROUND OF THE INVENTION

To provide a vacuum for a pneumatic brake booster, the interior of which is divided into at least one vacuum chamber and one working chamber, vacuum pumps are used which draw in residual air from the vacuum chamber and expel it to the atmosphere. Usually the automotive industry uses vane pumps or variable geometry vane pumps here. In principle these have a great deal of friction and must be lubricated to achieve an acceptable service life. Vacuum pumps with vanes driven by the internal combustion engine of the motor vehicle are therefore connected to the oil circuit of the combustion engine. However a significant proportion of the power emitted by the combustion engine must be used to drive such a pump. This also applies even when the vacuum is already fully formed in the chamber to be evacuated. Therefore it is useful to drive the vacuum pump with electrical energy and only switch it on when the absolute pressure in the vacuum chamber rises above a predetermined value.

Furthermore in vehicles with electric or hybrid drives, the vacuum pump (sometimes) cannot be driven by the combustion engine. Therefore in these vehicles, electrically driven vacuum pumps are used.

Equipping such an electrically driven pump with a lubricant circuit or connecting it to such a circuit would entail a disproportionally high expense. Thus for use in motor vehicles with brake systems with electrically driven vacuum pumps, only dry-running vacuum pumps can be used. For this in vane pumps the self-lubricating material graphite is used, from which the vanes can be produced with the necessary precision with high expense. Therefore efforts have been focused on using a diaphragm pump for electrical provision of a brake vacuum.

A generic motor-pump assembly is already known from DE 10 2007 005 223 A1, which is incorporated by reference. The automotive industry imposes very high requirements in relation to the acoustic comfort of motor vehicle components, and requires suppliers to provide robust, durable pumps with very low noise emission. To meet these requirements, in the known motor-pump assembly, the outlet channels are arranged in the working chamber covers and in the pump housing such that air expelled from the working chambers is conducted into an interior of the pump housing surrounding the crank drive. Furthermore an air outlet unit is provided which allows a low-noise expulsion of air from the interior by deflection of the air. The interior, also called the crank chamber, serves as a sound damping chamber since the expelled air is not conducted directly to the atmosphere. By deflecting the air in the air outlet unit, the noise level can be further substantially reduced so that blow-out noise is almost avoided.

SUMMARY OF THE INVENTION

Due to the increasing use of vehicles with electric drives, the acoustic requirements for the motor-pump assembly are rising further.

Therefore an aim of the present invention is to provide a motor-pump assembly which takes into account the rising requirements in relation to acoustic comfort.

This is achieved according to an aspect of the invention in that between each connecting rod eye and the roller bearing, a resilient decoupling is provided which damps a transmission to the roller bearing of vibrations in the connecting rod shank which occur on a force direction change on the rotation of the crank drive. Using the resilient decoupling according to the invention therefore the noise which occurs in the roller bearing by a force direction change on the rotation of the crank drive—in particular by overcoming the bearing play—and which is transmitted to an eccentric via the roller bearing can be minimized or eliminated.

An advantageous embodiment of the invention provides that for resilient decoupling, the roller bearing is provided resiliently embedded in the connecting rod eye. Thus the vibrations occurring on the rotation of the crank drive are only transmitted damped to the roller bearing.

Preferably the resilient decoupling can be provided as an elastomer layer between the connecting rod eye and an outer ring of the roller bearing. The seating of the roller bearing in the connecting rod eye can in this way be achieved with no further components. Furthermore as a result a low bearing play can be provided in the roller bearing.

According to an advantageous embodiment of the invention the roller bearing can easily be integrated in the connecting rod eye in that the elastomer layer is created by injection molding around the roller bearing placed in the connecting rod eye.

A further advantageous alternative embodiment of the invention provides that to receive the roller bearing, a connecting rod ring is provided which is resiliently embedded in the connecting rod eye. Thus the connecting rod ring which is preferably made of metal can form the press joint to the roller bearing, and the bearing can be fixed as previously by pressing into the connecting rod. Thus this production step can also be carried out in existing assembly lines without modification.

In a simple manner the connecting rod ring is provided preferably fixed by injection molding with the elastomer layer.

According to an advantageous embodiment of the invention, a lock can be provided between the connecting rod ring and connecting rod eye, whereby the fixing of the bearing can be ensured.

According to an advantageous embodiment, a simple lock is achieved if a mechanical lock is provided between the connecting rod ring and connecting rod eye. This is preferably provided as a bayonet lock.

A further advantageous embodiment of the invention provides that a resilient lock is provided between the connecting rod ring and connecting rod eye.

The resilient lock is preferably formed by undercuts in the connecting rod ring into which the elastomer layer can flow for locking.

A further improvement of the locking can be achieved according to a preferred embodiment in that on an inside of the connecting rod eye, protrusions are provided which are surrounded by the elastomer layer for locking.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed description when read in connection with the accompanying drawing. Included in the drawings are the following figures:

FIG. 1 a known motor-pump assembly in longitudinal section;

FIG. 2 a working diaphragm with fixed connecting rod of a first embodiment example according to the invention of a motor-pump assembly in a spatial depiction;

FIG. 3 a section through the connecting rod eye of the connecting rod in FIG. 2;

FIG. 4 a working diaphragm with fixed connecting rod of a second embodiment example according to the invention of a motor-pump assembly in spatial depiction;

FIG. 5 a section through the connecting rod eye of the connecting rod according to FIG. 4;

FIG. 6 a section through a connecting rod eye of a connecting rod of a third embodiment example according to the invention of a motor-pump assembly, and

FIG. 7 a section through a connecting rod eye of a connecting rod of a fourth embodiment example according to the invention of a motor-pump assembly.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a known motor-pump assembly 1 in longitudinal section which comprises a pump 2 with a pump housing 5 and an electric motor 3 driving the pump 2, wherein the motor 3 can be formed for example as a DC motor.

The pump 2 is provided as a double diaphragm pump with two opposing working diaphragms 4 which are each clamped between the pump housing 5 and a working chamber cover 6 and thus delimit a working chamber 7. The working diaphragms 4 are movable in opposition to each other by means of a crank drive 8, which for each working diaphragm 4 has an eccentric 9 and a connecting rod 10. The working chamber cover 6 has an upper cover 11 and a lower cover 12 which are welded, riveted or screwed together in an air-tight manner.

Inlet and outlet valves (not shown) are provided in the working chamber covers 6. The air expelled from the outlet valve is conducted via an outlet channel in the working chamber cover 6 to an outlet channel in the pump housing 5 which are connected air-tightly by means of a sealing element. The two outlet channels in the pump housing 5 open into an inner chamber 22 of the pump housing 5, the so-called crank chamber, which surrounds the crank drive 8. An air outlet unit 13 provided in or on the pump housing 5 allows a low-noise blow-out of air from the inner chamber 22 so that the inner chamber 22, which is also called the crank chamber, serves as a sound-damping chamber. The air outlet unit 13 comprises a non-return valve 20 having a one-piece or multipiece valve body 18 which prevents a back flow of air already expelled and the penetration of liquid or gaseous substances into the crank chamber 22.

In addition the air-borne noise on expulsion of the air from the inner chamber 22 is reduced in that the air outlet unit 13 has a filter element 17 arranged in a filter housing 14, through which the air escapes to the atmosphere. Furthermore the air outlet unit 13 comprises an air outlet cover 15, an air outlet closing cap 16 and a valve body 18, and is provided as a pre-mountable assembly. The air outlet cover 15, the air outlet closing cap 16 and the filter housing 14 are each attached with screw elements 19, 21. As is evident, the filter housing 14 is riveted to the air outlet cover 15. To deaden the sound, further means can be provided which are advantageously integrated in the air outlet unit assembly 13. For this the air outlet unit 13 can have an intermediate floor by means of which the air is deflected repeatedly as it flows through the air outlet unit 13. Furthermore several filter elements can be provided in the air outlet unit 13.

When the air pressure in the interior 22 of the pump 2 is greater than the atmospheric pressure surrounding the pump 2, the non-return valve 20 opens in that the valve body 18 lifts at least partly from the continuous bores 23 in the filter housing 14 and the air can escape from the pump housing 5 to the atmosphere through openings (not shown) in the air outlet closing cap 16 and through the filter element 17.

Furthermore on the pump housing 5 is provided a connection not shown via which for example a connected brake booster is evacuated.

It is further evident from FIG. 1 that a motor shaft 24 of the electric motor 3 is mounted in a first bearing (not shown) arranged in the motor 3, and in a second bearing 25, wherein the second bearing 25 is held partly by a motor housing 26 and partly by the pump housing 5. Thus an advantageous centering of motor 3 and pump 2 is achieved. The motor shaft 24 in this embodiment example serves simultaneously as an eccentric shaft 27 which carries the crank drive 8 with the eccentrics 9 and connecting rods 10. However a separate design of motor shaft 24 and eccentric shaft 27 is known.

The working diaphragm 4 separates the working chamber 7 from the crank chamber 22 and is firmly connected with a tappet 28, wherein the preferably non-deformable tappet 28 is injection molded with the resiliently deformable material of the diaphragm 4. Thus in the vicinity of the tappet 28, a portion 29 which is difficult to deform is produced in the center of the working diaphragm 4 and transforms towards the outside into an easily deformable portion 30, which in turn transforms towards the outside into a diaphragm bead 31 which is connected firmly and air-tightly with the pump housing 5. The tappet 28 can either be injection-molded with the material of the connecting rod 10, firmly connected with the connecting rod 10 by means of a weld or threaded connection, or provided integrally with the connecting rod 10. The connecting rods 10 are mounted movably on the eccentrics 9 by means of roller bearings 32 in the form of ball bearings.

The embodiment examples described below of a motor-pump assembly according to the invention differ from the known motor-pump assembly 1 described in FIG. 1 substantially only in the structure of the connecting rods, so that the description of the remaining structure of the motor-pump assembly can be omitted. In other words, the connecting rods according to the invention can be used in the known motor-pump assembly 1. However their use is not restricted to the motor-pump assembly 1 described according to FIG. 1, but in principle can also be provided in other assemblies.

The same components carry the same reference numerals.

Due to the increased use of vehicles with electric drives, the acoustic requirements imposed on the motor-pump assembly 1 are rising, so that the object to be achieved is to meet the growing requirements for acoustic comfort.

A force direction change in a connecting rod shank 37 of the connecting rod 10 occurs twice on every rotation of the crank drive 8. Due to the bearing play in the roller bearing 32 in the form of a ball bearing, an outer ring 35 of the roller bearing 32—which in known assemblies is press-fitted with a connecting rod eye 33 of the connecting rod 10—impacts with high dynamic on the roller body 36 and a rotating inner ring 34, wherein the excitations occurring are transmitted to the eccentric 9.

Therefore in all four embodiment examples described according to FIGS. 2 to 7, between the connecting rod eye 33, 33′, 33″ and the roller bearing 32, a resilient decoupling is provided which eliminates or damps a transmission to the roller bearing 32 of vibrations in the connecting rod shank 37 which occur on a force direction change on the rotation of the crank drive 8.

For this the embodiments provide that for resilient decoupling, the roller bearing 32 is resiliently embedded in the connecting rod eye 33, 33′, 33″ so that the vibrations occurring on rotation of the crank drive 8 are not transmitted or only transmitted damped to the roller bearing 32.

FIG. 2 shows a working diaphragm 4 with fixed connecting rod 10 of a first embodiment example according to the invention of a motor-pump assembly 1 in spatial depiction, wherein FIG. 3 shows a section through the connecting rod eye 33 of the connecting rod 10. It is evident from FIG. 3 in particular that the resilient decoupling is provided as an elastomer layer 38 between the connecting rod eye 33 and the outer ring 35 of the roller bearing 32. In this way the seat of the roller bearing 32 in the connecting rod eye 33 is implemented with no further components and a low bearing play can be provided in the roller bearing 32.

The roller bearing 32 is easily fixed in the connecting rod eye 33 by injection molding with the elastomer layer 38 around the roller bearing 32 placed in the connecting rod eye 33.

A second alternative embodiment is shown in FIGS. 4 and 5, wherein FIG. 4 shows the working diaphragm 4 with fixed connecting rod 10 in spatial depiction, and FIG. 5 shows a section through the connecting rod eye 33 of the connecting rod 10 according to FIG. 4.

This alternative embodiment, in contrast to the first embodiment example, provides that to receive the roller bearing 32, a connecting rod ring 39 is provided which is resiliently embedded in the connecting rod eye 33. The embedding is easily achieved by injection molding with the elastomer layer 38 around the connecting rod ring 39. Thus the connecting rod ring 39, which is preferably made of metal, provides the press joint to the outer ring 35 of the roller bearing 32 and the bearing can be fixed as previously by pressing into the connecting rod 10, without any modification of existing assembly lines being required. With this embodiment of the bearing fixing it is not necessary to degrease the outer ring 35 before installation or injection molding.

Also the subsequent press fitting prevents any lubricant present in the roller bearing 32 from escaping on embedding of the connecting rod ring 39.

Two further embodiment examples are shown in FIGS. 6 and 7. These differ from the second embodiment example according to FIGS. 4 and 5 in that a lock is provided between a connecting rod ring 39′, 39″ and the connecting rod eye 33′, 33″, whereby the fixing of the roller bearing 32 can be ensured.

As evident from the section through the connecting rod eye 33′ according to FIG. 6, a mechanical lock is provided between the connecting rod ring 39′ and the connecting rod eye 33′, which lock is provided for example as a bayonet lock which is elastomer-bonded by means of the elastomer layer 38′.

In contrast, FIG. 7 shows in cross section through the connecting rod eye 33′ of the fourth embodiment example a resilient lock between the connecting rod ring 39″ and connecting rod eye 33″. The resilient lock is formed by undercuts 41 in the connecting rod ring 39″ into which the elastomer layer 38″ can flow for locking, wherein a further improvement of the locking can be achieved in that on an inside of the connecting rod eye 33″, protrusions 40 are provided which are also surrounded by the elastomer layer 38″ for locking. It is also possible here that the connecting rod ring 39″ is a roller bearing inner ring.

LIST OF REFERENCE NUMERALS

1 Motor-pump assembly

2 Pump

3 Motor

4 Working diaphragm

5 Pump housing

6 Working chamber cover

7 Working chamber

8 Crank drive

9 Eccentric

10 Connecting rod

11 Upper cover

12 Lower cover

13 Air outlet unit

14 Filter housing

15 Air outlet cover

16 Air outlet closing cap

17 Filter element

18 Valve body

19 Screw element

20 Non-return valve

21 Screw element

22 Interior

23 Continuous bore

24 Motor shaft

25 Bearing

26 Motor housing

27 Eccentric shaft

28 Tappet

29 Portion

30 Portion

31 Sealing bead

32 Roller bearing

33 Connecting rod eye

34 Inner ring

35 Outer ring

36 Roller body

37 Connecting rod shank

38 Elastomer layer

39 Connecting rod ring

40 Protrusion

41 Undercut 

1.-12. (canceled)
 13. A motor-pump assembly for providing pressure for a brake actuation device of a motor vehicle brake system with a pneumatic brake booster, in particular a vacuum brake booster, comprising a pump and an electric motor driving the pump, wherein the pump is provided as a double diaphragm pump with two opposing working diaphragms which are each clamped between a pump housing and a working chamber cover and thus delimit a working chamber and which are movable by a crank drive having an eccentric and connecting rods, and wherein the connecting rods each have a connecting rod shank and a connecting rod eye and are mounted movably on the eccentrics by roller bearings, wherein between each connecting rod eye and the roller bearing, a resilient decoupling is provided which damps a transmission to the roller bearing of vibrations in the connecting rod shank which occur on a force direction change on the rotation of the crank drive.
 14. The motor-pump assembly as claimed in claim 13, wherein for resilient decoupling, the roller bearing is provided resiliently embedded in the connecting rod eye.
 15. The motor-pump assembly as claimed in claim 14, wherein the resilient decoupling is provided as an elastomer layer between the connecting rod eye and an outer ring of the roller bearing.
 16. The motor-pump assembly as claimed in claim 15, wherein the elastomer layer is created by injection molding around the roller bearing placed in the connecting rod eye.
 17. The motor-pump assembly as claimed in claim 13, wherein to receive the roller bearing, a connecting rod ring is provided which is resiliently embedded in the connecting rod eye.
 18. The motor-pump assembly as claimed in claim 17, wherein the connecting rod is provided fixed by injection molding with the elastomer layer.
 19. The motor-pump assembly as claimed in claim 17, wherein a lock is provided between the connecting rod ring and the connecting rod eye.
 20. The motor-pump assembly as claimed in claim 19, wherein a mechanical lock is provided between the connecting rod ring and the connecting rod eye.
 21. The motor-pump assembly as claimed in claim 20, wherein the mechanical lock is a bayonet lock.
 22. The motor-pump assembly as claimed in claim 19, wherein a resilient lock is provided between the connecting rod ring and the connecting rod eye.
 23. The motor-pump assembly as claimed in claim 22, wherein the resilient lock is formed by undercuts in the connecting rod ring into which the elastomer layer can flow for locking.
 24. The motor-pump assembly as claimed in claim 23, wherein on an inside of the connecting rod eye, protrusions are provided which are surrounded by the elastomer layer for locking. 